[eschaton]

I don't think this ist an apt characterization at all.

Downtowns across the country have of course revitalized. But just as important have been the revitalization of the core urban residential neighborhoods which managed to survive urban renewal. In virtually every city (even struggling rust belt cities) there will be at least a few of these neighborhoods which are on the upswing. And in high demand areas, basically all the close-in areas which aren't horrible ghettos begin to turn - and even those ghettos have huge institutional pressure to gentrify, such that developers begin encroaching on them block by block.

In contrast, in most metros, outer city neighborhoods are all stagnant to declining. The only examples I can think of where gentrification and/or redevelopment occurs in neighborhoods further out is if there's a secondary employment center (usually a major university) located on the fringes of the city.

So the new "doughnut" is more Downtown+urban core wealthy, outer urban+inner suburban as dis-invested, and exurbs as wealthy.